1. Field
Exemplary embodiments of the present invention provide a light emitting device and a method of fabricating the same, and more particularly, to a light emitting device having a wavelength converting layer and a method of fabricating the same.
2. Discussion of the Background
Current light emitting diodes (LEDs) can be made lightweight and compact, and have advantages of energy reduction and long lifetime. Accordingly, LEDs have been used as backlight sources for various types of display devices including cellular phones, and the like. Since a light emitting device having an LED mounted therein, i.e., an LED package, can implement white light having a high color rendering property, it is expected that the LED will be utilized for general illumination by substituting for white light sources such as fluorescent lamps.
Meanwhile, there are various methods of implementing white light using LEDs, and a method is generally used in which white light is implemented by combining an InGaN LED that emits blue light of 430 to 470 nm and a phosphor that can convert the blue light into long wavelength light. For example, the white light can be implemented by combining a blue LED and a yellow phosphor excited by light from the blue LED to emit yellow light or by combining a blue LED and green or red phosphors.
Conventionally, a white light emitting device has been formed by applying a resin containing a phosphor into a recess region of a package having LEDs mounted therein. However, as the resin is applied into the package, the phosphor is not uniformly distributed in the resin, and the resin is not uniformly formed to have constant dimensions between the light emitting devices. As a result, a color variation according to viewing angles easily occurs in a light emitting device, and it is difficult to obtain uniform chromaticity between light emitting devices fabricated in the same process.
Accordingly, studies have been conducted to develop a technique for forming a wavelength converting layer with a uniform thickness by attaching a wavelength converting sheet on an LED or using a conformal coating technique. However, since light emitted from the LED does not have a uniform luminous intensity distribution according to a viewing angle, when the wavelength converting layer with the uniform thickness is formed, a color variation according to a viewing angle may occur.
FIG. 1 shows an example of luminous intensity distribution according to a viewing angle of a horizontal blue LED.
Referring to FIG. 1, the luminous intensity is highest in a vertical direction from an LED, i.e., at a position at which the viewing angle is zero degrees, and the luminous intensity decreases as the viewing angle increases. The luminous intensity is generally highest at the position at which the viewing angle is zero degrees even when the shape of a substrate or epitaxial layer is controlled or a surface texture is used in order to modify the shape of the LED and improve light extraction efficiency.
Since the luminous intensity distribution of light emitted from the LED varies depending on the viewing angle, when a wavelength converting layer with a uniform thickness is formed on the LED, the luminous intensity distribution of light obtained by mixing blue light and wavelength-converted light together also varies depending on the viewing angle. Moreover, the ratio of the blue light to the mixed light is relatively increased at a viewing angle at which the intensity of the blue light is greater. As a result, a color variation according to the viewing angle occurs.